As a conventional slide rail device for vehicle, a device is known which is equipped with a left and right pair of lower rails extending in a forward/rearward direction which include a plurality of lock grooves, extending vertically while being open at the lower ends thereof; upper rails which support the seating portion of a seat and are slidably supported by the left and right pair of lower rails, a lock-release lever which is partly accommodated in the internal spaces of each upper rail and which are supported by each upper rail to be rotatable in the vertical direction between a locked position and an unlocked position, a locking portion which fits into the lock grooves when the lock-release lever is positioned at the locked position and which comes out downwardly from the lock grooves when the lock-release lever is positioned at the unlocked position, and a biaser (spring) which biases and rotates the locking lever toward the locked position.
Therefore, when an occupant applies no operating force to the operating lever, the slide positions of the seat and the upper rails with respect to the lower rails are maintained since the lock-release levers which are held in the locked position by the biasing force of the biaser and the locking portion is engaged with some of the lock grooves. On the other hand, upon an occupant rotating the lock-release lever to the unlocked position against the biasing force of the biaser, the locking portion is released from the engagement with the lock grooves to thereby allow the seat and the upper rails to slide relative to the lower rails.